1. Field of the Invention
This invention relates to a novel and improved method for manufacturing a yarn bobbin, as well as to a bobbin obtained by such method.
More specifically this invention relates to a method for manufacturing yarn bobbins particularly suitable for winding high count yarns, and essentially formed by a cylindrical hollow core having flanges removably fastened to opposite ends thereof.
2. Description of Prior Art
To removably secure the flanges to a bobbin core is an already well known technique, particularly suitable when high count yarns are to be wound thereon, i.e. when no danger exists that the yarn may get engaged or "pinched" between the core ends and the flanges during reciprocating motions of related opposite surfaces, due to different stresses that are exerted on the flanges by the wound yarn in an axial outward direction, when the bobbin is relatively full and relatively empty. Obviously, when using high count yarns, a given relative motion of the opposite surfaces is allowed, provided that an opening wider than the yarn size is not formed between the mating surfaces under the highest possible stress.
The removably fitted flanges, which are usually secured by means of screws to front sides, of the core, have the advantage of allowing for a quick and easy replacement thereof in case of breakage.
However, heretofore a heavy drawback is shown by heretofore known bobbins having removable flanges have the disadvantage, due to the fact that they require a thick walled core, or at least thicker ribs extending in a radial direction with respect to the core axis, to allow for drilling threaded holes on the front sides of the core, as required to accomodate screws for securing the flanges. This results in a substantial waste of material, since the end portion only of the ribs is utilized, as well as in undue increases of core weight and moment of inertia, not always accurately balanced with respect to the core axis, and accordingly requires a more difficult balancing operation of the core and the entire bobbin.